Resonant generation of difference harmonics due to intersubband transitions in a biased superlattice

The difference harmonic susceptibility due to intersubband transitions in a superlattice subjected to uniform electric field is calculated. The transitions between uncoupled ground states and tunnel-coupled excited states are considered in the framework of the effective mass approximation. The spectral dependencies of the susceptibility and modification of the nonlinear response with variation of the applied voltage are presented. The efficiency of transformation of the double-frequency near-IR pump into THz radiation is also discussed and the enhancement of transformation due to the THz waveguide effect has been found.